OS X: Keyboard shortcuts are great: they can save you tons of time and effort—assuming you know them all. If you don't know every keyboard shortcut under the sun, Eve is an OS X utility that teaches them to you. Every time you perform a function or command with the mouse for which there's a corresponding keyboard shortcut, Eve will display the shortcut on screen so you'll learn it and remember to use it next time.

For example, in the Finder, if you click the "Go" menu and select "Connect to Server," Eve will pop up an alert in upper right corner of your screen with the Eve logo and "Command K" in the box so you'll remember to do it next time. Eve remembers which ones you've performed, and only reminds you once in a while so it doesn't become too much of a nag, but it definitely lets you know that you could have performed the same action you just did with the mouse using only the keyboard.

Right now, Eve supports shortcuts in the Finder, Chrome, Safari, and Mail.app, but the developer is working on support for "almost all apps" in the near future—most likely starting with common shortcuts that work similarly in just about every application. Still, if you want to pick up some keyboard shortcuts you may not already know, Eve is a great utility to help you learn.